8V sounds strange.... The driver is inside the battery carrier, so if you measure 8V at the carrier, the that would mean 8V to the LED, which can't really be.
I have the CNQG version of that clone, it's performance is about 2/3 of the original TK35 in terms of flux (light output/lumens) and spot intensity.
Related threads: TK35 clone - NotFenix NotTK35 - TheKlone35 (driver mod)